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Health Team

Tight fit more important than a second mask to prevent COVID-19 spread

Posted February 19, 2021 12:54 p.m. EST
Updated February 19, 2021 1:22 p.m. EST

— The Centers for Disease Control and Prevention says you should double up on wearing masks.

University of North Carolina researchers put that idea to the test, running trials to see how much extra protection, if any, double-masking would provide. On Friday morning, they released their findings.

In a briefing, they shared their research on the effectiveness of masks overall, the importance of mask fit, and the extra benefits of double-masking.

The CDC now recommends double masking for ultimate safety

Fit is most important

“You really need to address fit and make sure whatever you’re wearing is tight to your face," said Dr. Phillip Clapp, assistant professor in the Department of Pediatrics.

According to Clapp, simply ensuring a single mask is fitted can increase effectiveness by 20%.

A mask that isn't fitted allows air and aerosols to pass through any gaps, which decreases protection against COVID.

Double-masking does provide increased protection

The tests indicated that double-masking provides increased protection, provided the masks are fitted.

“With double-masking, we saw a 15% increase [in protection], just by double-masking procedure or surgical masks," said Clapp.

Furthermore, double-masking can provide extra protection, depending on how the wearer layers their masks.

For example, layering a cloth mask on top of a surgical mask showed a roughly 40% increase in efficiency. However, layering a surgical mask on top of a cloth mask didn't provide similar protection.

Mask frames, which help ensure a good tight fit, also provided extra benefits.

However, even double-masking doesn't compare to wearing an N-95 mask.

But wearing two surgical masks, and adding a frame or brace around the face to prevent leaks and create a good fit, reached 97% effectiveness in one test.

In short, extra layers do provide extra protection – but it's very important to make sure your mask fits, or else the leakage will allow aerosols through.

Finally, Dr. Emily Sickbert-Bennett, director of infection prevention at UNC, addressed the most important kind of 'double-masking.'

"The most important 'double-masking' is when you and the person you are with are both wearing a mask," she said.

So whether or not you decide to double-mask, one of the most effective ways of preventing the spread of COVID is simply by everyone wearing at least one mask.

Is wearing a mask or 'double-masking' dangerous?

Some people have raised concern over whether or not wearing a mask could decrease their oxygen levels. Could double-masking, then, have a potential drawback?

Clapp and Sickbert-Bennett said they do not believe this is a concern.

Clapp said that what people are worried about is re-breathing their own air, which increases carbon-dioxide and decreases oxygen.

However, he said, those concerns are not backed by the science of how masks work.

"When you’re wearing a mask, the volume of air inside this breathing space is very low. So when I take a breath in, I’m pulling in air from the outside," he said.

That's the whole purpose of masks, he explained. They are meant to filter out particles from the outside air as you breathe air through the masks.

"So you’re bringing in fresh air in addition to the small amount of air that you’ve exhaled previously," he said.

Sickbert-Bennett said, “From all of our medical doctor colleagues that have reported on this, that is not going to be a concern.”

When can we stop wearing masks?

Since COVID is transmitted by respiratory droplets, masks are key to preventing spread.

"By everyone wearing masks consistently, I think that’s the best way we’re going to end the pandemic," said Sickbert-Bennett.

She said when transmission slows, the community can reassess when it's time to hang our masks up for good.

Until then, we can increase our protection by ensuring our masks are fitted – and, if we choose, by double-masking.

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